Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
  • G01V8/00—Prospecting or detecting by optical means
  • G01V8/02—Prospecting
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
  • G01J5/0003—Radiation pyrometry, e.g. infrared or optical thermometry for sensing the radiant heat transfer of samples, e.g. emittance meter
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
  • G01J5/60—Radiation pyrometry, e.g. infrared or optical thermometry using determination of colour temperature
  • G01J5/602—Radiation pyrometry, e.g. infrared or optical thermometry using determination of colour temperature using selective, monochromatic or bandpass filtering

Definitions

• the present invention relates to thermal imaging, and more specifically, it relates to a method for detecting an underground object surrounded by a host material.
• Dual Band Infrared (DBIR) imaging has numerous advantages over conventional thermal imaging, which utilizes only a single band.
• Conventional thermal imaging is difficult to interpret for three reasons: 1. It yields imprecise information that is insensitive to the subtle heat flow anomalies produced by subsurface objects. 2. It fails to distinguish between surface emissivity clutter and temperature-related heat flows. 3. Spatially-varying surface reflections (emissivity-related noise), typically equivalent to a one or two degree Celsius temperature difference, cannot be removed by using a single passive thermal IR band even when used in conjunction with another active-laser reflectance IR band.
• DBIR imaging was used to detect buried land mines by exploiting temperature differences between the mine site and the surrounding soil.
• the present invention provides clear clutter-free images of heated underground objects displayed in three spatial dimensions, which 1. Characterize the subsurface-object size, shape, volume, thickness, depth, location and thermal inertia, relative to the surrounding host materials. 2. Provide clutter-free maps of subsurface objects displayed in three spatial dimensions. 3. Allow detection of deeper objects, at depths to twenty times the object width or diameter.
• Cumulative extraneous effects e.g., noise produced by clutter
• Planck's law states that radiation emitted by a source can be related to its temperature.
• Planck's law states that the radiant emittance of a surface is proportional to emissivity times absolute temperature to the power of (50/ wavelength in microns).
• a power law thermal model provides the physical rationale for ratioing narrow LR bands involving calculating mathematical ratios using signals with equations derived from Planck's law to produce signal ratios. These signal ratios are insensitive to the natural surface emissivity and provide enhanced thermal responsivity. The derivation of this model is given in the Appendix of LeSchack and Del Grande, "A Dual-Wavelength Thermal Infrared Scanner as a Potential Airborne Geophysical Exploration Tool," Geophysics, VOL.41, No 6 (December 1976) P.1318-1336, incorporated herein by reference.
• this model is used to determine signal ratios that are in turn used to remove surface emissivity noise.
• the emissivity of surface materials is highly variable from one land area to another.
• the ratio of signals at two or more wavelengths can be used to obtain highly precise surface-temperature measurements that depend very little upon emissivity variations. For example, temperature differences as small as 0.2 degrees C can be obtained by using the present invention.
• the emissivity ratio variations are very small.
• quantitative temperature measurements are made using signal ratios that are calibrated against a standard blackbody source.
• emissivity factor noise
• Clutter may include, e.g., shadows, tracks, stains, disturbed terrain, holes, vegetation, foreign objects, foreign materials, foreign soils, water, cool air pools and roughness variations.
• Qutter of a specular nature may be identified and removed by image processing because it has a distinctive emissivity signature.
• the emissivity factor produced by reflected-infrared signal noise relates to the ability of surfaces which produce clutter to emit radiant energy less than that of a black body at the same temperature and differently at one wavelength than at another.
• a black body is an ideal surface that absorbs and emits all radiation without reflection.
• the present invention provides a method for detecting an underground object surrounded by a host material, where the detection is accomplished by using thermal inertia diagnostics, which removes both surface and subsurface foreign-object clutter.
• the host material is analyzed using visible, temperature and thermal inertia imagery to characterize the contrasting features of the host material from those of the object.
• An area of the structure is then scanned simultaneously at two or more different wavelengths of radiation to produce a time sequence of images taken at different times during day and night or at different months during the year. The time sequence of images is processed into signal ratios that are used to remove clutter.
• Obtaining a temperature versus time history is important to determine the size, shape, volume, depth, type and location of the object.
• images cannot be interpreted very easily without also studying the time history of infrared image ratios, which eliminate clutter of a thermal nature.
• Other informative maps may be generated by repeating temperature survey measurements at two or more different times when the diurnal or seasonal temperature spreads provide the greatest contrast for the object and host material, compared to subsurface foreign objects and foreign materials which produce thermal-image clutter.
• Thermal image clutter may be identified and removed by mapping the maximum minus the minimum temperature spread from coregistered day minus night, or autumn minus spring, temperature maps.
• Thermal image clutter is produced by foreign objects, and materials, such as: disturbed terrain, animal holes, roots, water, mud and rocks which resist diurnal and seasonal temperature changes differently than the sought-after object and host material.
• the diurnal or seasonal temperature spread provides a unique signature to identify and remove thermal image clutter when combined with the different location, size, shape, volume, depth, and inverse thermal inertia which distinguishes foreign objects and materials from the targeted object.
• the corrected temperature data is used to generate corrected temperature and temperature-spread maps. Corrected temperature and temperature-spread maps are color-coded images that show color patterns of conducted heat generated by objects which heat and cool at different rates relative to the surrounding materials.
• T [( ⁇ 5 / ⁇ 10 )(T) 5 1/[( ⁇ 5 / ⁇ o)(T) 5 ] Ave ⁇ ag ⁇ (6)
• ⁇ T m the measured relative temperature spread contrast
• ⁇ T C the relative temperature spread contrast
• ⁇ T vary inversely as the thermal inertia, P, or resistance to temperature spread, and directly as the fractional volume, f of the object, (o), and 1-f of the host, (h) for a column of unit area and unit volume.
• the relative temperature spread contrast ⁇ T is calculated for column 1 with the host material and the object minus column 2 with the host material only, divided by the temperature spread of the host material only column.
• An embodiment of the process steps of the present invention is provided in Figure 1. A selection is made of a host and a subsurface object site environment (10). Note that the host and subsurface object site environment are naturally heated, not artificially heated.
• a survey is carried out of the host and said object site by: simulating the temperatures of said host and said object site (12), calculating the thermal inertias of said host and said object site (14), and computing the temperature spreads (e.g., twice-daily and bi-yearly) of the host and said object site (16).
• a determination is made whether the thermal inertia of the object site is distinguishable from that of the host (18).
• a change is made of the environment of the host and the object site if the temperature spread of the object site is not distinguishable from that of the host (20). The previous steps are repeated until the object site is distinguishable from that of the host (18).
• the host and object site are then scanned at different times with two different IR wavelengths (22) and a spatial sequence is recorded of dual-band IR images at different times (24).
• a record is made of the object and host temperature, thermal inertia and temperature spread (26).
• a calculation is made, on a computer workstation (28) using image-processing code (30) of signal ratios and differences to form temperature, emissivity-ratio and corrected-temperature maps. Emissivity, temperature and temperature-spread maps are then coregistered (32). Temperature maps and temperature-spread maps are then corrected (34).
• Foreign object thermal clutter is removed from the temperature- spread maps (36). Object location, size and shape are determined from the temperature maps (38).
• thermal inertia contrast can be located for solid or semi-solid objects by detecting disturbed, moistened or displaced earth materials, which surround them. For example, this applies to subsurface walls, foundations, aquifers, ditches, burial sites, landmines, munitions, leaky pipelines and foxholes.
• thermal inertia contrast can be located for hollow, or partially empty structures by detecting undisturbed, or compacted earth materials, which surround them.
• the shallow drain end is less than 1 meter (3.3 feet) deep, north of the Dome of the Rock.
• the deep end of the 136 meter (446 feet) long drain is over 15 meters (49 feet) deep, as it descends under the Large Cistern, at the southeast corner of the Dome of the Rock platform.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geophysics (AREA)
• Radiation Pyrometers (AREA)
• Geophysics And Detection Of Objects (AREA)
• Investigating Or Analyzing Materials Using Thermal Means (AREA)

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• 2004
  • 2004-01-30 EP EP04816718A patent/EP1590692A2/de not_active Withdrawn
  • 2004-01-30 CA CA2514982A patent/CA2514982C/en not_active Expired - Lifetime
  • 2004-01-30 WO PCT/US2004/002822 patent/WO2005047935A2/en not_active Ceased
  • 2004-01-30 US US10/769,217 patent/US7157714B2/en not_active Expired - Lifetime
• 2005
  • 2005-07-28 IL IL169978A patent/IL169978A/en active IP Right Grant

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